Predicting submarine buoyancy motion is a prerequisite for exploring and studying the laws of submarine buoyancy motion control and submarine buoyancy safety. The numerical calculation method and calculation process of submarine buoyancy motion were introduced in detail. The turbulence model and discrete scheme in the numerical calculation method were optimized. The uncertainty of numerical calculation was analyzed and the results of numerical calculation were verified based on the model floating test′s results, what′s more, it was found that the reliability of numerical calculation was proved and the numerical calculation results were in good agreement with the experimental results, thus verifying the feasibility of the numerical calculation method. The numerical calculation method and test can provide reference and reference for the research of submarine floating movement.